Antenna radomes which include heating wires are generally known. Such radomes may include a grid of high resistance Inconel wires for heating the radome to prevent the formation of ice. Problems arise, however, in that the heating wires tend to increase the reflection coefficient at the surface of the radome to incident electromagnetic wave energy at the operating wavelength of the antenna. Thus, the level of energy transmitted through the radome decreases from that which would be transmitted in the absence of the heating wires. Also, depending on the spacing between adjacent wires and the operating wavelength, the free space antenna pattern may be adversely affected by the radome wires, for example, by the generation of grating lobes in the antenna pattern. Appropriate precautions must therefore be taken with respect to the heating wire grid arrangement. To ensure system compatibility, it may be necessary to provide suitable compensation to signals transmitted or received by the antenna as a function of the antenna scan angle relative to the radome. It may in some cases even be impossible to obtain adequate radome heating capability owing to limitations imposed on the heating wire configuration at a given operating wavelength and degree of scan.
It is also generally known that highly conductive wires (e.g. copper), when arranged in a certain pattern on or parallel to a major surface of an antenna radome, will serve to enhance the impedance match between the radome material and the surrounding space. A radome having a thickness that is small compared to the antenna's operating wavelength will exhibit a capacitive susceptance to incident electromagnetic wave energy. The inherent capacitive susceptance of the radome material can be cancelled by introducing a corresponding inductive susceptance to the radome by the use of conductive wires that follow a meandering path in a plane parallel to the surface of the radome.
As far as is known, no attempts have been made to use conductive wires arranged on or in a radome for purposes of impedance matching and also as a means for generating heat sufficient to de-ice the radome during severe weather conditions.
It is, therefore, an object of the present invention to overcome the above and other shortcomings in the known heated radome constructions.
Another object of the invention is to provide an antenna radome construction that affords the desirable features of a heated radome and also is well matched to the surrounding space at a given operating wavelength and over a wide range of antenna scan angles.
A further object of the invention is to provide a heated and matched antenna radome suitable for use with precision antenna installations at environmentally severe locations.
Another object of the invention is to provide a radome construction with both heating and matching capabilities, and one that does not necessitate complex means for antenna signal compensation over a given scan angle range.
Yet another object of the invention is to provide an antenna radome with both heating and matching capabilities, that exhibits a relatively high frequency bandwidth ratio with respect to a given antenna operating wavelength.